Biostatistics Questions
- A cohort study is conducted to assess the association between clinical characteristics and the risk of stroke. the study involves n= 1250 participants who are free of stroke at the study start. Each participants is assessed at study start (baseline) and every year thereafter for five years. the table below displays data for hypertension.
Hypertension at baseline and two years later
Two years later: Not hypertensive Two Years later: Hypertensive
Baseline: Not hypertensive 850 148
Baseline: Hypertensive 45 207
status measured at baseline and hypertension status measured two years later.
a) compute the prevalence of hypertension at baseline
b) compute the prevalence of hypertension at two years.
c) Compute the cumulative incidence of hypertension over two years.
Question 2 : Hypertension at baseline and stroke five years later
Free of stroke at five years Stroke
Baseline: Not hypertensive 952 46
Baseline: Hypertensive 234 18
The data shown above were collected in the study described in problem 1 relating hypertensive status measured at baseline to indicate stroke over five years.
a) Compute the cumulative incident of stroke in this study.
b) Compute the cumulative incidence of stroke in patients classified as hypertensive at baseline.
c) Compute the cumulative incidence of stroke in patients free of hypertension at baseline.
d) Compute the risk difference of stroke in patients free of hypertension.
e) Compute the relative risk of stroke in patients with hypertension as compared to patients free of hypertension.
f) Compute the population attributable risk of stroke due to hypertension.
A national survey is conducted to assess the association between hypertension and stroke in persons over 75 years of age with a family history of stroke. Development of stroke is monitored a over 5- years follow- up period. The data are summarized below and the numbers are in the million.
Hypertension and the Development of stroke
Developed Stroke Did not develop stroke
Hypertension 12 37
No hypertension 4 26
a) Compute the cumulative incidence of stroke in persons over 75 years of age.
b) Compute the relative risk of stroke in hypertensive as compared to non-hypertensive persons.
C) Compute the odds ratio of stroke in hypertensive as compared to non-hypertensive persons.